Locking damper positioner

ABSTRACT

A damper positioner includes a lead screw to move the damper blade and a screw lock selectively engageable with the screw to permit rotation of the screw but prevent unintended rotation.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

BACKGROUND OF THE INVENTION

The present invention relates to a damper for controlling the flow offluid in a duct and, more specifically, to an apparatus for controllingthe position of the blade of a damper.

A damper is a valve or plate that stops or regulates the flow of fluidinside a duct, chimney, air handler, or other fluid handling equipment.The fluid is commonly a gas, such as air, but may be a liquid or vaporand the duct may be under positive or negative pressure. Referring toFIG. 1, a common type of fluid control damper 20 is a butterfly dampercomprising a frame 22 and one or more blades 24 each supported by anaxle 26 which is journaled for rotation in the opposing walls of theframe.

The frame 22 typically comprises a length of duct similar incross-section to the ducting 28 in which the damper is to be installed.The frame 22 may be round or rectangular and may have one or two flanges30 for connecting the damper to the contiguous sections of ducting 28.On the other hand, particularly in lower pressure systems, thecross-section of one end of the frame may be expanded and thecross-section of other end of the frame may be reduced to enable theends of the frame to, respectively, slip over and into the ends of thecontiguous sections of ductwork.

The substantially planar blade 24 of the damper is rotatable to aposition normal to the flow of fluid, substantially blocking flow offluid in the duct. Dampers may include seals that engage the blade whenit is oriented normal to the fluid flow to minimize the flow of fluidbetween the periphery of the blade and the interior surface 32 of theframe. When the blade is rotated to an orientation substantiallyparallel to the flow of fluid, the planar blade produces a minimalpressure drop and the flow through the damper is substantiallyunrestricted. Blade orientations between the two extreme orientationsproduce pressure drops of varying magnitude and restrict flow to varyingdegrees.

The position of the blades(s) of a damper may be mechanically ormanually controlled. Electric motors, hydraulic cylinders and pneumaticcylinders are commonly used to position the blades of dampers,particularly in automated systems. However, many dampers are used inapplications where the damper is only rarely adjusted after the initialbalancing of the system's flows. In these applications, mechanicaloperation of the damper may not be economically justifiable and dampersare commonly equipped for manual operation. A manually operatedbutterfly damper typically includes a handle 34 affixed to the axle thatrotatably supports the blade 24. By moving the handle a user can rotatethe blade to adjust the fluid flow through the damper. While manualadjustment of the damper is typically less expensive than mechanicalactuation, dampers are often located in areas with limited or difficultmanual access to the damper's handle.

Typically, a damper is adjusted to balance the flows in the ductwork orto limit the flow in a particular duct. Once the adjustment iscompleted, the position of the damper's blade is secured against furthermovement. Manual adjustment handles commonly utilize a friction lock,such as a screw 36 and wing nut 38 that can be tightened to increase thefriction between the handle 34 and the handle's mounting 40 on theframe. Friction locks provide infinite adjustment of the blade'sposition but the position of the blade can be altered if the handle isbumped by a person or equipment. Referring to FIG. 2, manually operateddampers are sometimes equipped with sector locks comprising a pluralityof holes 52 in the handle 50 or the handle's mounting. A screw or theshackle of a lock inserted thorough a hole in the mounting and one ofthe holes in the handle locks the handle and the blade in position. Theposition of the sector locked blade is substantially secure againstaccidental movement but the adjustment is limited to a few positionswhich may not provide sufficiently fine adjustment of the blade'sposition for a particular application.

Maintaining control of the damper's blade during adjustment is alsoimportant, particularly in industrial applications. Typically, a damperis adjusted while fluid is flowing in the ductwork. When either afriction lock or a sector lock of a manually operated damper isreleased, the user must maintain a grip on the handle to preventmovement of the blade often while trying to measure the pressure dropacross the damper. If the user releases or inadvertently moves thehandle, the flow of fluid in the damper and in other parts of the systemcan change significantly. A change in the flow rate in the ductwork candisrupt manufacturing processes, damage products and, in some cases,present a safety hazard.

What is desired, therefore, is an apparatus for controlling the positionof the blade of a damper which is economical to manufacture, suitablefor retrofitting an existing damper or for use with a new damper,enables manual adjustment in areas with limited access, provides finelevels of adjustment, secures the blade in the adjusted position andprevents uncontrolled movement of the blade during adjustment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a damper arranged for manual adjustment.

FIG. 2 is a perspective view of a damper handle with sector locking.

FIG. 3 is a perspective view of a butterfly damper with a screw actuatedadjustment.

FIG. 4 is an elevation view of the damper of FIG. 3 with the blade inthe closed position.

FIG. 5 is an elevation view of the damper of FIG. 3 with the blade inthe open position.

FIG. 6 is a perspective view of the head of the lead screw of FIG. 3 andthe screw lock in the locked position.

FIG. 7 is a perspective view of the head of the lead screw of FIG. 3 andthe screw lock in the unlocked position.

FIG. 8 is a perspective view of a second example of a damper positionerand lead screw lock.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A damper is a valve enabling regulation of the flow of fluid inside aduct, chimney, air handler, or other fluid handling equipment. The fluidis commonly a gas, such as air, but may be a liquid or vapor. Referringin detail to the drawings where similar parts are identified by likereference numerals, and, more particularly to FIG. 3, an exemplarydamper 60 comprises a frame 22 including a central aperture 23 that istypically similar in cross-section to the ducting in which the damperwill be installed. The frame of the exemplary damper 60 is round butdampers are also commonly rectangular or square in cross-section. Theexemplary damper 60 has a flange 30 at either end of the frame forconnecting the damper to contiguous portions of the ductwork. However,dampers may have a flange at only one end of the frame and some dampersdo not have a flange for connecting to adjacent ducting. Thecross-section of the aperture of the damper may be expanded or reducednear the ends of the frame to enable the ends of the contiguous ductingto, respectively, slip into or over the ends of the damper's frame.

The exemplary damper 60 is a butterfly valve or damper and includes arotatable blade 24 supported by an axle 26 which is journaled forrotation in the wall on opposing sides of the frame. The axle may besupported in the frame by bearings or bushings (not shown) and the framemay be equipped with seals (not shown) to prevent leakage where the axlepasses through the wall of the frame. To control the flow of fluid inthe duct, the blade can be rotated between a position where the plane ofthe blade is normal to the flow of fluid and a position where the planeof the blade parallel to the fluid flow. When the blade is orientednormal to the fluid flow, the flow of fluid is blocked or, at least,restricted to leakage between the periphery of the blade and theinternal surface(s) 32 of the frame. Some dampers also include seals onthe inner surface 32 of the frame to seal any gap between the peripheryof the blade and the periphery of the frame's aperture. When the bladeis oriented parallel to the flow of fluid, the planar blade produces aminimal pressure drop and the flow through the damper is maximized.Blade orientations between the two extreme orientations produce varyingmagnitudes of pressure drop and flow restriction.

Referring also to FIGS. 3 and 4, the position of the blade 24 of theexemplary damper is manually adjustable. The blade 24 of the damper isaffixed to the axle 26 which is journaled in the wall of the frame onopposite sides of the aperture 23. The axle 26 is affixed to a lever 62proximate a first end of the lever. Preferably, the orientation of thelever parallels the plane of the blade 24 providing a visual referenceof the orientation of the blade in the frame. The position of the leverand, therefore, the orientation of the blade is controlled and adjustedby a lead screw 64 which is connected to the lever 62 proximate thesecond end of the lever. The lead screw 64 is in threaded engagementwith an anchor 66 that is pivotally attached 68 to the lever 62 enablingthe angle of screw, relative to the lever, to change as the lever movesthe damper between the open position and the closed position.

The lead screw is rotatably journaled in a second anchor 70 proximatethe second end of the lead screw. The second anchor is pivotallyattached 72 to a mounting plate 74 which is, in turn, secured to theexterior of the frame 22 by screws 76. The lead screw is rotatable inthe anchor but is restrained against translation by one or more snaprings 71, collars and/or shoulders bearing on the anchor. As illustratedin FIGS. 3 and 4, by rotating the lead screw 64, a user can manuallyadjust the blade's position between the fully closed position 78 and thefully open 80 position. Since the screw is always engaged with the leverand the frame, the movement of the blade is under control throughout theadjustment of the blade's position. In addition, the threads of the leadscrew are preferably self-locking to resist rotation of the screw whenthe user is not actively applying torque to the screw.

Referring also to FIGS. 6 and 7, the lead screw 64 includes a head 82located at an end of the screw. The head preferably includes anon-circular portion 84, a tapered or conical portion 86 and a manuallygraspable portion 88. The graspable portion 88 enables a user to gripand rotate the lead screw with the fingers and, preferably, includes aknurled surface or other surface treatment to improve the user's grip.Alternatively, the graspable portion of the head may include provisionsfor coupling to a motor or other actuator for remote adjustment of thedamper. The non-circular portion 84 includes one or more lobes or facets85 enabling engagement and rotation with a tool having a complementaryinterface. For example, a non-circular portion having a hexagonalcross-section, as illustrated in FIG. 7, enables engagement and rotationwith a socket wrench 86. Referring also to FIG. 8, the non-circularportion of the lead screw head 100 may have a less common cross-section,such as an ellipse 104, requiring a tool with a special shape to engagelimiting access to the positioner.

Dampers are commonly located in areas where there is limited accessmaking engagement with a tool difficult. The tapered portion 84 of thehead is preferably frustoconical and aids in guiding the tool intoengagement with the non-circular portion of the head.

The damper positioner includes a lead screw lock 90 that shields thehead 82 of the screw from inadvertent contact and locks the screwagainst unintentional rotation. The lead screw lock comprises a body 92,106 including portions defining a socket 94, 108. The socket has across-section complementary to the cross-section of the non-circularportion of the head and a depth enabling engagement of the socket with afirst length 95A of the non-circular portion 84 of the head of the leadscrew. Engagement of the facets 85 or lobes 105 of the lead screw headby the surfaces of the complementarily shaped socket in the bodyprevents independent rotation of the lead screw and the body 92, 102 ofthe screw lock.

Preferably, a second length 95B of the non-circular portion of the headprotrudes beyond the body 92 enabling a tool to engage the non-circularportion of the head while the body is engaged with head.

A spring 96 or other resilient member urges the body 92 which isslidable on the lead screw toward the head end of the screw, urgingengagement of the socket with the non-circular portion of the head ofthe lead screw. Interaction of the complementary shapes of thenon-circular portion of the screw's head and the socket prevents thescrew from rotating independent of the socket. When a user wishes torotate the lead screw, the body 92 of the screw lock is displaced towardthe anchor, for example by the tool engaging the head of the screw,until the non-circular portion of the head is disengaged from the socketin the body of the screw lock enabling rotation of the head of the screwand adjustment of the damper's blade.

The body 92 of the screw lock 90 is prevented from rotating relative tothe anchor and, therefore, the frame of the damper. Referring to FIGS. 6and 7 the body 92 of screw lock may be secured against rotation relativeto the anchor and the frame by one or more pins 98 having one endportion affixed to the body 92 and a portion slidably fitted in anaperture 99 in the anchor. On the other hand, as illustrated in FIG. 8,one or more facets 102 or lobes on the periphery of the body 106slidably engaging the anchor 70 or the mounting plate will secure thebody against rotation relative to the anchor and permit disengagement ofthe body of the lock and the non-circular portion of the screw head.Interaction of the complementary shapes of the non-circular portion ofthe screw's head and the socket prevents the screw from rotatingindependent of the socket which is restrained against rotation relativeto the frame to avoid unintended movement of the damper blade frominadvertent contact with the screw.

The detailed description, above, sets forth numerous specific details toprovide a thorough understanding of the present invention. However,those skilled in the art will appreciate that the present invention maybe practiced without these specific details. In other instances, wellknown methods, procedures, components, and circuitry have not beendescribed in detail to avoid obscuring the present invention.

All the references cited herein are incorporated by reference.

The terms and expressions that have been employed in the foregoingspecification are used as terms of description and not of limitation,and there is no intention, in the use of such terms and expressions, ofexcluding equivalents of the features shown and described or portionsthereof, it being recognized that the scope of the invention is definedand limited only by the claims that follow.

I (we) claim:
 1. An apparatus for adjusting a blade of a damper, said blade affixed to an axle rotatably mounted in a frame of said damper, said apparatus comprising: (a) a lever affixed to said axle proximate a first end of said lever; (b) an elongate screw comprising a head portion, said screw in threaded engagement with a first anchor affixed to said lever remote from said first end, said screw rotatable but axially restrained in a second anchor affixed to said frame, rotation of said screw rotating said axle; and (c) a screw lock selectively engageable with said screw to selectively restrain rotation of said screw.
 2. The apparatus of claim 1 wherein said screw lock comprises a body defining a socket having a shape complementary to a shape of said head portion and axially movable relative to said screw to selectively engage said head portion in said socket, said body rotationally restrained.
 3. The apparatus of claim 2 further comprising a resilient member urging axial movement of said body and engagement of said socket with said head portion of said screw.
 4. The apparatus of claim 2 wherein said head portion includes a facet and said socket includes a complementary facet.
 5. The apparatus of claim 2 wherein said head includes a hexagonal portion and said socket defines a hexagon.
 6. The apparatus of claim 2 wherein said body is rotationally restrained by a pin affixed to said body and slidably engaging said second anchor.
 7. The apparatus of claim 2 wherein said body includes a peripheral facet slidably engaged with one of said frame and said second anchor.
 8. The apparatus of claim 1 wherein said head portion of said screw comprises: (a) a first portion engageable by a tool for rotating said screw; and (b) a conical second portion tapering to an end of said head portion to guide said tool into engagement with said first portion.
 9. The apparatus of claim 7 wherein said head portion includes a third portion separating said first portion and said conical second portion, said third portion facilitating manual rotation of said screw.
 10. An apparatus for selectively constraining rotation of a screw in an anchor, said screw including a head, said apparatus comprising: (a) a body defining a socket having a shape complementary to a portion of said head of said screw, said body axially slidable on said screw but rotationally restrained by said anchor; and (b) a resilient member urging said body toward said head to engage said head in said socket, engagement of said head and said socket restraining rotation of said screw relative to said body.
 11. The apparatus of claim 10 wherein said head portion includes a facet and said socket includes a complementary facet.
 12. The apparatus of claim 10 wherein said head includes a hexagonal portion and said socket defines a hexagon.
 13. The apparatus of claim 10 wherein said body is rotationally restrained by a pin affixed to said body and slidably engaging said anchor.
 14. The apparatus of claim 10 wherein said body includes a peripheral facet slidably engaged with said anchor. 